1. Field of the Invention
The present invention relates to an advanced humid air turbine power plant including a humidifying line to humidify gas (air) supplied to a gas turbine.
2. Description of the Related Art
In an advanced humid air turbine, combustion gases contain moisture and have a larger heat transfer coefficient and larger specific heat than air due to differences in physical variables therebetween, such as the coefficient of viscosity and the Plandtl number. Therefore, the thermal load in a high-temperature component of the gas turbine, such as a turbine blade, is increased in comparison with an ordinary gas turbine. Correspondingly, the high-temperature component of the gas turbine must be cooled in a stepped-up manner. However, if air cooling is employed as in the ordinary gas turbine, a very large amount of cooling air is required, which results in a lowering of the temperature of a main stream gas and a reduction in thermal efficiency of the gas turbine. For that reason, in the advanced humid air turbine, the high-temperature component of the gas turbine requires to be cooled using a coolant having a higher cooling capability than air, and it is proposed to employ a method of utilizing, as the coolant, a part of humidified air generated in a humidifying tower. Because of containing moisture, the humidified air has a larger heat transfer coefficient and larger specific heat than air and is able to develop a higher cooling capability. As a result, the high-temperature component of the gas turbine can be effectively cooled with a relatively small amount of coolant without requiring additional equipment.
One known technique related to such an advanced humid air turbine (HAT) power plant is disclosed in, for example, JP,A 11-257006. The known technique proposes a cooling method of bleeding, from lines for supplying air and humidified air both used for combustion, the air and the humidified air at a plurality of locations in the respective lines, mixing them to prepare a coolant, and cooling the high-temperature component of the gas turbine with the coolant. As a practical way, the proposed method comprises the steps of bleeding a part of compressed air from a compressor and a part of humidified air from a humidifying tower, mixing them in a mixer, and supplying a mixed coolant to a cooling channel in the gas turbine.